A. Field of the Invention
The present invention relates to an apparatus for acquiring and displaying 3 dimensional (3-D) image data by scanning a plurality of sub-regions of a target scan region and a method for acquiring and displaying ultrasound 3-D images. More particularly, the present invention relates to an ultrasound diagnosis apparatus that can set a 3-D scan target region in a preliminary scan mode (hereinafter, “pre-scan mode”) and acquire 3-D image data (hereinafter, “volume data”) by sequentially scanning a plurality of sub-divided scan regions (hereinafter, “sub-scan region”) of the target region and a method for acquiring volume data of the target region by initially scanning a sub-scan region that contains or borders a reference plane of the pre-scan mode, or the closest sub-scan area.
B. Background of the Invention
An ultrasound image diagnosis apparatus transmits and receives ultrasound through a plurality of ultrasound transducers installed in an ultrasound probe to and from a target in an object in a plurality of directions in order to display the image of the target on a monitor. Since an ultrasound image diagnosis apparatus can easily obtain and display a two dimensional image or a three dimensional image in real time by simply touching an ultrasound probe to a patient's body surface, it is widely used as an apparatus for diagnosing the status of a target organ in a patient's body.
Conventionally, these devices must move their probes' 1-D array transducers in a direction orthogonal to an array direction or rotate the 1-D array of transducers in order to acquire 3-D image data by using an ultrasound probe having a plurality of transducers arrayed in one dimension (1-D) by transmitting and receiving ultrasound over a 3-D area of a target organ in an object. 3-D image data are generated by rendering the acquired 3-D data (hereinafter, “volume data”).
Recently, 2-D array ultrasound probes have been used. The 2-D array ultrasound probe includes a plurality of transducers arrayed in two dimensions (2-D) (i.e., an azimuth direction and an elevation direction). By using a 2-D array ultrasound probe, it becomes possible to electrically control whole operations of transmissions and receptions of ultrasound over a 3-D region of a target in order to significantly shorten volume scan time of the target and improve operability of an ultrasound examination.
However, in ultrasound transmission and reception, it has been necessary to repeat ultrasound transmission and echo reception for extremely long times in order to acquire volume data of a desired 3-D region. The required time for performing a respective ultrasound transmission and reception is determined by the acoustic velocity of the ultrasound transmission into an object and the maximum imaging depth. Accordingly, much time is required to acquire volume data of a sufficient spatial resolution.
To address this problem for real-time display of image data, a technique has been developed to simultaneously receive a plurality of echo ultrasound signals reflected from a target in an object. This is defined as a parallel simultaneous receiving method. By applying the parallel simultaneous receiving method to a 3-D scan (volume scan), it becomes possible to reduce 3-D data acquisition time. However, a very large number of parallel receptions are required in order to perform a volume scan for an organ that moves in accordance with each heart beat or cardiac cycle, such as a patient's heart. To realize such a large number of parallel receptions, very complicated circuit arrangements for ultrasound devices have been required. This is a serious problem for manufacturing in view of cost performance.
To solve the above-mentioned problem, U.S. Pat. No. 6,544,175 has proposed a method for collecting volume data by dividing a portion of a diagnosis subject into a plurality of 3-D sub-regions in order to successively scan the plurality of 3-D sub-regions while synchronizing with a cardiac cycle. Hereinafter, in order to assist a simple understanding of this specification, such a method for acquiring volume data by sequentially scanning a plurality of regions by referencing and synchronizing to ECG (electric cardiogram) signals of a patient's heart beats is simply referred to as a “triggered volume scan” method.
The conventional triggered volume scan method performs a plurality of volume scans sequentially over each of a plurality of 3-D sub-regions of a subject's volume scan region during a prescribed period and stores the acquired sub-volume data with the cardiac cycle data after once displaying the newly acquired sub-volume data. When acquisition of sub-volume data for a plurality of 3-D sub-regions has completed, volume data for each volume scan regions is generated by combining each of the sub-volume data sets of the plurality of 3-D sub-regions at the same heart beat phases. The compounded 3-D image data are processed so as to generate 3-D image data, such as sequential volume rendering image data and multi planar reconstruction (MPR) image data at a desired slice plane. By doing so, it becomes possible to observe 3-D image data of a diagnosis object portion as a motion image.
The conventional triggered volume scan method designates a reference scanning plane and a volume scan region based on 2-D image data acquired by a single plane scan or a multi-plane scan, such as a bi-plane scan over a diagnosis object portion in a pre-scan mode performed before acquiring entire volume data over a volume scan region.
In the entire volume data acquisition mode, the volume scan area is divided into a plurality of 3-D sub-regions based on a prescribed interval between the sub-regions. Each of the plurality of 3-D sub-region is successively scanned in order to collect data for each sub-volume. By composing the collected sub-volume data, 2-D multi planar reconstruction image data (hereinafter “MPR image data”) at a reference scanning plane and 3-D image data are generated and displayed in a display unit. By monitoring the displayed MPR image data, it is judged whether acquisition of volume data of a volume scan region is correctly performed. If a problem is found, the acquisition of volume data is repeated.
Generally, the volume scan region of a diagnosis portion in an object is based upon a reference scanning plane in order to monitor the acquisition status of volume data for a volume scan region. Consequently, when an acquisition of sub-volume data of a plurality of 3-D sub-regions is started from a 3-D sub-area located at an edge portion of the volume scan region, it happens to display no MPR image data for the reference scanning plane while collecting sub-volume data of the plurality of 3-D sub-regions including the reference scanning plane. Thus it becomes impossible to display the most important diagnosis data until the acquisition of sub-volume data for the 3-D sub-regions is completed.
Thus, while the triggered volume scan method collects 2-D image data of the reference scanning plane by performing acquisition of 2-D image data with matching positions of two orthogonal cross-sections in the pre-scan mode, no display of MPR image data in the reference scanning plane acquired in the triggered entire volume mode occurs. Consequently, triggered volume scans cannot observe the initial view of a motion image of a diagnostic portion. This is a problem because the monitoring accuracy of the volume data is deteriorated. Furthermore, this increases monitoring burdens for an operator.